MySQL 表查询必备：基本操作详解

INSERT [INTO] table_name[(column [, column] ...)]VALUES (value_list) [, (value_list)] ...value_list: value, [, value] ...

create table students( -> id int unsigned primary key auto_increment, -> stunum int not null unique comment '学号', -> name varchar(20) not null, -> email varchar(20) -> );

insert into students values(1, 1001, 'Smith', '11111');

insert into students(stunum, name) values(1003, 'Mike');

insert... on duplicate key update column = value [, column = value] ...

insert into students(id, stunum, name) values(2, 1010, 'Jane') -> on duplicate key update stunum = 1010, name = 'Jane';

SELECT[DISTINCT] {* | {column [, column] ...}[FROM table_name][WHERE ...][ORDER BY column [ASC | DESC], ...]LIMIT ...

			create table exam_result(
			    -> id int unsigned primary key auto_increment,
			    -> name varchar(20) not null comment '姓名',
			    -> chinese float default 0.0 comment '语文成绩',
			    -> math float default 0.0 comment '数学成绩',
			    -> english float default 0.0 comment '英语成绩'
			    -> );

			insert into exam_result(name, chinese, math, english) values
			    -> ('Smith', 67, 98, 62),
			    -> ('Jane', 64, 78, 79),
			    -> ('Tiny', 76, 87, 77),
			    -> ('John', 89, 78, 90),
			    -> ('Mike', 90, 91, 93),
			    -> ('Lily', 82, 83, 89),
			    -> ('Klin', 60, 53, 59);

select id, name, math from exam_result;

select name, english from exam_result where english < 60;

select name, chinese from exam_result where chinese >= 80 and chinese <= 90;

select name, chinese from exam_result where chinese between 80 and 90;

select name, math from exam_result -> where math = 53 -> or math = 91 -> or math = 98;

select name, math from exam_result where math in(53, 91, 98);

select name from exam_result where name like 'J%';

select name from exam_result where name like 'J_';

select name, math, english from exam_result where english > math;

select name, chinese+math+english total from exam_result where chinese+math+english < 200;

  		select name, english from exam_result 
  		    -> where english > 80 and name not like 'M%';

  		select name, chinese, math, english, chinese+math+english total from exam_result
  		    -> where name like 'T%'
  		    -> or chinese+math+english > 200
  		    -> and chinese < math
  		    -> and english > 80;

select name, email from students where email is not null;

select null = null, null = 1, null = 0;

select NULL <=> NULL, NULL <=> 1, NULL <=> 0

select ... from table_name [where ...] order by column [asc|desc], [...];

select name, math from exam_result order by math asc;

select name, email from students order by email asc;

select name, math, english, chinese from exam_result order by math desc, english asc, chinese asc;

select name, chinese+math+english total from exam_result order by total desc;

				select name, math from exam_result 
				    -> where name like 'J%' or name like 'S%'
				    -> order by math desc;

			起始下标为 0
			
			从 0 开始，筛选 n 条结果
			select... from table_name [where ...] [order by ...] limit n;
			
			从 s 开始，筛选 n 条结果
			select... from table_name [where ...] [order by ...] limit s, n;
			
			从 s 开始，筛选 n 条结果，比第二种用法更明确，建议使用
			select... from table_name [where ...] [order by ...] limit n offset s;

select name, chinese, math, english from exam_result -> order by id limit 3 offset 0;

select name, chinese, math, english from exam_result order by id limit 3 offset 3;

select name, chinese, math, english from exam_result order by id limit 3 offset 6;

update table_name set column = expr [, column = expr ...][where ...] [order by ...] [limit ...];

update exam_result set math=80 where name='Jane';

update exam_result set chinese=80, english=70 where name='John';

select name, math, chinese+math+english total from exam_result order by total limit 3;

update exam_result set math = math + 30 order by chinese+math+english limit 3;

select name, math, chinese+math+english total from exam_result where name in('Klin', 'Jane', 'Smith');

update exam_result set english = english * 2;

delete from table_name [where ...] [order by ...] [limit ...];

delete from exam_result where name='Lily';

delete from employee;

truncate [table] table_name

truncate employee;

insert into table_name [(column [, column ...])] select ...

  		mysql> create table duplicate_table (id int, name varchar(20));

  		
  		mysql> INSERT INTO duplicate_table VALUES
  		    -> (100, 'aaa'),
  		    -> (100, 'aaa'),
  		    -> (200, 'bbb'),
  		    -> (200, 'bbb'),
  		    -> (200, 'bbb'),
  		    -> (300, 'ccc');

create table no_duplicate_table like duplicate_table;

insert into no_duplicate_table select distinct * from duplicate_table;

select count(*) from students;

select count(email) from students;

select count(english) from exam_result;

select sum(math) from exam_result;

select avg(chinese+math+english) 平均总分 from exam_result;

select max(chinese) from exam_result;

select min(chinese) from exam_result where chinese > 70;

select column1, column2, .. from table group by column;

select deptno, avg(sal), max(sal) from emp group by deptno;

select deptno, job, avg(sal), min(sal) from emp group by deptno, job;

select deptno, avg(sal) from emp group by deptno;

select deptno, avg(sal) from emp group by deptno having avg(sal) < 2000;

from > on> join > where > group by > with > having > select > distinct > order by > limit